1. Technical Field of the Invention
The invention concerns modified fibres and other polypropylene products like film, nets or casings and the procedure for their manufacture.
2. Description of the Prior Art
From the monography xe2x80x9cPolypropylene Fibresxe2x80x94Science and Technologyxe2x80x9d Elsevier Scientific Publ. Comp. 1982 and from U.S. Pat. No. 3,256,258, a procedure is known to produce polypropylene fibres with increased elasticity. The procedure consists of attaining a specific orientation of the fibres by the application of a relevant melt-drawing ratio (no more than 2.5) in the course of fibre forming and relaxation at 105-160xc2x0 C. during 30-60 minutes in the course of fibre processing. Fibres produced this way are characterized by a 100-700% elongation at break and 82% elasticity at 25% elongation.
International patent application PCT/US96/11085 and Polish Patents P.322371 and P.317596 disclose polyolefin composites with high surface lustre and impact resistance, designed for formed and extruder sheets, and shaped pieces. These products excepting polypropylene or polyethylene, contain elastomeric olefin copolymers. These composite thermoplastic olefins are manufactured by blending the single components in a blender and with further forming on a roller at elevated temperature or by extrusion.
The composites include the following components: polypropylene homopolymer or its copolymers with other polyolefins, olefin polymers formed by a one-or two step sequential polymerization, copolymers of ethylene with C3-C8 xcex1-olefins and elastomeric copolymers of ethylene, and C3-C8 xcex1-olefins polymerized with metalocene catalysts.
From the Polish Patent Application P.3 18763 fibres and non-wovens are produced from a blend of a highly crystalline polypropylene and a statistic propylene-ethylene block copolymer. The tenacity of such product is comparable with standard polypropylene non-wovens, however, its softness is higher.
U.S. Pat. Nos.: 4,302,557, 4,336,212, 4,336,350, 4,379,888, 4,454,303, 4,481,334, 4,499,241, 4,537,935, 4,701,496, 4,835,218, 5,352,518 describe composites containing a non-elastic polymer like polypropylene and polyethylene, an elastic polyolefin like polyvinylacetal and an elastomer like an ethylene-xcex1-olefin copolymer. These composites are designed for the manufacture of films shrinking at low temperature.
In xe2x80x9cVlakna a Vextilxe2x80x9d Vol. 1(1) p. 11-16, 1994; xe2x80x9cFibres and Textiles in Eastern Europexe2x80x9d Vol.2(2) p.42-43, 1994 and Vol.2(3) p.38-42, 1994; Japanese Patent No. 85.81316, Belgian Patent No. 895355, German Patent No. 2832218 and U.S. Pat. No. 4,055,608 procedures are described for the manufacture of modified polypropylene fibres by forming same from blends of polypropylene with other known miscible polymers like polyethylene and its non-elastic polyolefin copolymers, polyamides, copolyamides, and polyesters. Fibres made from modified polypropylene have better dyeability, better mechanical properties and higher moisture sorption.
Modified fibres and other polypropylene products like film, nets and designs made according to the invention constitute a polymeric blend of standard polypropylene and an elastomer with melting point above 80xc2x0 C., preferably 100-180xc2x0 C., the melt flow index in the 1-60 g/10 min. range and density within 0.85-0.95g/cm3. The elastomer constitutes a branched copolymer of ethylene and/or polyolefin copolymer with ethylene and/or higher alkene groups in the main chain. The weight proportion of polypropylene to the elastomer is between 99.9:0.1 to 0.1:99.9.
According to the invention the procedure to produce fibres and other polypropylene products like film, nets or casings consists in the blending of standard polypropylene granulates in a weight proportion between 99.9:0.1 to 0.1:99.9 with an elastomer granulate with a melting point not lower than 80xc2x0 C. preferably 100 to 180xc2x0 C., and a melt flow index in the 1-60 g/10 min range and density with in 0.85-0.95g/cm3. The elastomer constitutes a branched copolymer of ethylene and/or a polyolefin copolymer with ethylene and/or higher alkene groups in the main chain. Fibres and other products are formed from the blend of granulates at a temperature within 190-290xc2x0 C. according to known manufacturing procedures.
The procedure to produce fibres and other polypropylene products like film, nets or casings consists also in the blending of standard polypropylene in a weight proportion between 99.1:0.1 to 0.1:99.9 with an elastomer with a melting point not lower than 80xc2x0 C. preferably 100 to 180xc2x0 C., and a melt flow index in the 1-60g/10 min range and density within 0.85-95g/cm3. The elastomer constitutes a branched copolymer of ethylene and/or a polyolefin copolymer with ethylene and/or higher alkene groups in the main chain. The obtained blend is melted at 190-260xc2x0 C., and from the melt a strand or band is extruded, which after solidification at 15-30xc2x0 C. is granulated and possibly vacuum-dried at 60-80xc2x0 C. Fibres and other polypropylene fibres are formed from the obtained granulate according to known manufacturing procedures.
In the manufacturing procedures according to the invention the elastomer is preferably applied as a concentrate obtained by blending 50-99% of the elastomer with the granulate of a polyolefin carrier like polypropylene or polyethylene. The blend is then regranulated at 190-260xc2x0 C. The concentrate mixed in the weight proportion of 1-99% with standard polypropylene. The merit of the modified fibres and other polypropylene products according to the invention is the dependence of their properties on the content of the elastomer component in the polymer blend. With the increase of the elastomer content, the elasticity of products increases while the elongation module and the elastic strain during elongation decrease. Modified polypropylene fibres containing up to 30 wt % of the elastomer manifest mechanical properties like module and elastic strain resembling polyamide fibres. Fibres with 30-50 wt % of the elastomer component are characterized by significantly improved elastic properties. Before drawing they resemble elastomer polyurethane fibres in respect to tenacity, module and strain in the elastic deformation area. They are distinguished by a 700-800% elongation at break, increased to 80-85% elasticity for 1 cycle and 70-80% for 5 cycles at elongation xcex5=50% and by elasticity module lowered to 10 cN/tex and strain at 50% elongation lowered to 1 cN/tex. Adequate properties for elastomeric monofilaments having a linear density of 44 dtex of Lycra type are: elongation at break-500%, elasticity at elongation xcex5=50% for 1 and 5 cycles-100%, elasticity module appr. 0.8cN/tex and strain at elongation xcex5=50% -about 0.4 cN/tex. After drawing, these fibres are in respect of module comparable to low-module polyamide filaments. Non-oriented fibres with 50 wt % elastomer content resemble much more high-elastic elastane fibres than those with a content of elastomer below 50 wt %. The characteristic of other modified polypropylene products is similar depending upon the content of the elastomer. Up to 30 wt % content of the elastomer, the fibres and other products, according to the invention, have good resistance properties in comparison with standard polypropylene products and, besides, a much improved elasticity and are subject to deformation in the elastic area.
The advantage of the method according to the invention is the possibility to form modified fibres and other polypropylene fibres on existing production facilities. A further advantage of the modified polypropylene products is the possibility to dye from dye liquors.
Modified fibres and other polypropylene products as well as the procedures to their manufacture can be applied in the chemical fibres industry and for the manufacture of products with special properties. particularly improved softness and elasticity.
Following methods were applied in the testing of polymers, fibres and film:
Melting pointxe2x80x94the melting temperature range of the sample was determined using Boetnis microscope at temperature increase 4-5xc2x0 C./min,
Melt Flow Index using a plastometer. The weight of the extruded sample was measured at 230xc2x0 C. with 21.1 N load throng a 2 mm capillary during 3 minutes
Titrexe2x80x94according to Standard PN-EN ISO 2060
Tenacity of the filaments "sgr", and elongation at break xcex5rxe2x80x94according to Standard PN-EN ISO 2062
Young""s modulus of elasticityxe2x80x94according to Standard PN-84/P-04669
Resilience of the filamentsxe2x80x94according to Standard PN-84/P-04667
Tenacity and elongation at break for film was tested according to Standard PN-8 1/C 89092
Resilience of filmxe2x80x94film bands 15 mm wide 100 mm long (between clamps) were extended and released with 50 mm/mm speed. The relaxation time both for strain and release was 60 sec. The measurement was performed in one cycle for deformation xcex5 and, after the relaxation at release, the constant deformation xcex5p was measured as the difference between the length after relaxation and the initial length.
The resilience was calculated from the formula   Resilience  =                    ϵ        -                  ϵ          p                    ϵ        xc3x97    100  